title: A novel bench-scale column assay to investigate site-specific nitrification biokinetics in biological rapid sand filters.
abstract: A bench-scale assay was developed to obtain site-specific nitrification biokinetic information from biological rapid sand filters employed in groundwater treatment. The experimental set-up uses granular material subsampled from a full-scale filter, packed in a column, and operated with controlled and continuous hydraulic and ammonium loading. Flowrates and flow recirculation around the column are chosen to mimic full-scale hydrodynamic conditions, and minimize axial gradients. A reference ammonium loading rate is calculated based on the average loading experienced in the active zone of the full-scale filter. Effluent concentrations of ammonium are analyzed when the bench-scale column is subject to reference loading, from which removal rates are calculated. Subsequently, removal rates above the reference loading are measured by imposing short-term loading variations. A critical loading rate corresponding to the maximum removal rate can be inferred. The assay was successfully applied to characterize biokinetic behavior from a test rapid sand filter; removal rates at reference loading matched those observed from full-scale observations, while a maximum removal capacity of 6.9 g NH4(+)-N/m(3) packed sand/h could easily be determined at 7.5 g NH4(+)-N/m(3) packed sand/h. This assay, with conditions reflecting full-scale observations, and where the biological activity is subject to minimal physical disturbance, provides a simple and fast, yet powerful tool to gain insight in nitrification kinetics in rapid sand filters.
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, Miljøevej 113, 2800 Kgs. Lynby, Denmark. Electronic address: kaot@env.dtu.dk.
authors.forename: K
authors.initials: K
authors.lastname: Tatari
authors.forename: B F
authors.initials: BF
authors.lastname: Smets
authors.forename: H-J
authors.initials: HJ
authors.lastname: Albrechtsen
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism; D005374:Filtration; D058465:Nitrification / Q000502:physiology*; D012822:Silicon Dioxide; D014865:Waste Disposal, Fluid
chemical_list: D064751:Ammonium Compounds; D012822:Silicon Dioxide
keywords: Activity; Ammonium; Biofilter; Drinking water; Loading; Removal rate